Floating Titan
A team of researchers from the Australian RMIT University has developed a material they call a "floating metal polymer metamaterial with an open-cell lattice structure." It is based on titanium, which cannot float in the form of an alloy with high corrosion resistance Ti-6Al-4V – it is 4 times denser than water. Such an alloy can be used to make stationary marine structures resistant to winds and storms, but now scientists have also taught him how to swim.
Making non—floating material float is very simple - according to Archimedes' law. It is necessary to make a volumetric thin-walled structure from it, the weight of which will be less than the weight of the water displaced by it. But in this case, the approach does not work – any hole leads to the fact that water begins to fill the internal volume, the structure becomes heavier and sinks. And they want to make objects out of titanium to work under extreme loads, for which significant deformation will be an invariable part of normal operation.
Floating Titan
Scientists have printed a complex structure from titanium by baking metal powder with a laser – it is a cube of tubes with walls only 0.2 mm thick and internal channels from 2.5 to 4 mm in diameter. Expanding polyurethane foam was pumped into the tubes, which filled the entire space. This is how the metamaterial turned out: titanium, polyurethane, plus air bubbles in the foam form a single whole. An important point is that water flows freely through this structure, but cannot get inside the tubes. During the tests, the new material showed excellent buoyancy in both fresh and salt water. Then the cube was broken and returned to the water – even after the formation of deep cracks and partial destruction, the buoyancy remained. It disappeared only when the cube was crushed so much that its volume almost disappeared – the resulting lump of titanium became heavier than water again. That is, if you make something from such a material, it will fail long before it starts to sink, and you can have time to take action.
